1. Field of the Invention
The present invention relates to the fabrication and handling of precast concrete panels. More particularly, the invention is directed to anchors designed to be embedded in concrete sandwich panels when the panels are formed.
2. Description of the Prior Art
Precast concrete construction includes the plant prefabrication of concrete wall panels. Tilt-up construction is a job-site form of precast concrete construction involving the prefabrication of concrete wall panels on either a building floor slab or a temporary casting slab. Anchors are commonly used in both plant and job-site concrete wall panel fabrication, whereby lifting hardware is used to grasp an anchor embedded in each concrete panel and lift the panel from horizontal to a vertical position. The panel is then carried by a mobile crane to its final position where it is temporarily braced until tied into a roof and floor system to become an integral part of the completed structure.
One type of panel finding increasing use in tilt-up construction is the concrete sandwich panel, a composite panel of two relatively thin outer concrete wythes or layers and an inner insulation wythe or layer located between the concrete wythes. The placement of the insulation between the two concrete wythes protects the insulation from damage and reduces both the construction and maintenance costs of the completed structure.
A disadvantage of conventional anchors is that they are not suitable for use in concrete sandwich panels, since such prior art anchors cannot be properly retained within the insulation layer, resulting in the dangerous condition of the anchor being pulled from the sandwich panel upon lifting. Further, placement of prior art anchors within the concrete of the sandwich panel typically results in the spalling or fracturing of the relatively thin concrete wythes.
Accordingly, there is a need for an anchor which is adapted for use with a concrete sandwich panel. More particularly, there is a need for an anchor which is adapted for being securely retained within a concrete sandwich panel to facilitate lifting thereof without damaging the outer concrete wythes.